What is a concrete mix ratio?
A concrete mix ratio states the proportions of cement, sand and coarse aggregate, usually in that order. 1 : 2 : 4 means one part cement, two parts sand and four parts stone on the stated measurement basis. Water is controlled separately through the water/cement or water/binder ratio.
A concrete grade describes strength. It does not, by itself, determine the material quantities or prove that a batch will achieve that strength.
Calculate a concrete mix →Concrete mix ratio table: M10 to M30
In the Indian M-grade designation, the number is the characteristic strength of a 150 mm concrete cube at 28 days, expressed in MPa (N/mm²). It is not a cement-to-aggregate ratio.
| Grade / strength | Cement : sand : stone | How to interpret it |
|---|---|---|
| M10 · 10 MPa | 1 : 3 : 6 | Common nominal shorthand; review permitted nominal-mix limits. |
| M15 · 15 MPa | 1 : 2 : 4 | Common nominal shorthand; review permitted nominal-mix limits. |
| M20 · 20 MPa | 1 : 1.5 : 3 | Common nominal shorthand. A designed M20 mix can have different proportions. |
| M25 · 25 MPa | Design mix | No universal 1 : 1 : 2 recipe. Use material properties and trials. |
| M30 · 30 MPa | Design mix | Calculate water, binder and aggregates for the actual design brief. |
The first three ratios are common nominal volume shorthand, also listed in UltraTech’s ratio guide. They are not presented here as guaranteed strengths or as a substitute for IS 456 batching provisions.
IS 456 clause 9.3 limits its nominal-mix provision to M20 or lower. Table 9 gives mass-based aggregate limits and maximum water per 50 kg cement, with conditions on the fine/coarse split. The nominal mix calculator explains those limits. M25, M30, M45 and M50 need a designed mix; copying a fixed ratio from a grade table is insufficient.
How are cement, sand and aggregate ratios measured?
A ratio by mass
For a purely arithmetic example, 1 : 2 : 4 by mass gives 50 kg cement, 100 kg sand and 200 kg stone. Those quantities do not tell you the finished volume or achieved grade. The materials, water, air, compaction and measured yield still matter.
A ratio by loose volume
The same notation by loose volume uses equal-sized measuring containers. A bucket of cement does not weigh the same as a bucket of sand or stone. Sand bulking and moisture also change what fits in a container. Do not substitute kilograms for litres in a volume recipe.
Absolute volume in a designed mix
The lab uses mass and specific gravity to account for one cubic metre. For example, 31.5 kg cement at a specific gravity of 3.15 occupies 10 litres of absolute solid volume. Loose cement also has spaces between particles. Its bucket volume is therefore a different measurement.
How much cement, sand and aggregate are needed for 1 m³?
The answer depends on the design. These three examples use the calculator’s declared material assumptions; the M20 example demonstrates minimum cement content, M25 demonstrates strength selection, and M30 demonstrates moisture correction.
| Example | Cement | Sand, wet | Stone, wet | Mixer water | Admixture |
|---|---|---|---|---|---|
| M20 example | 300.00 | 749.58 | 1,237.25 | 157.73 | 3.00 |
| M25 example | 328.60 | 722.47 | 1,239.72 | 157.73 | 3.29 |
| M30 example | 375.54 | 711.76 | 1,243.03 | 124.46 | 3.76 |
Each linked example lists its exposure, slump, aggregate moisture and other inputs. Because those briefs differ, this table is not a controlled comparison of grade alone. Use the full mix design calculator to keep the other inputs fixed when comparing grades.
How to turn designed quantities into a ratio
Divide each SSD ingredient mass by the total binder mass. In the default M30 lab example, binder is 375.54 kg, SSD sand is 684.65 kg and SSD stone is 1,236.88 kg per m³. Dividing by 375.54 gives 1 : 1.82 : 3.29 by SSD mass. This is the result for those inputs, not a universal M30 ratio.
For a blend containing fly ash or GGBS, the lab labels the denominator as total binder. For batching, use the moisture-corrected weights and mixer water rather than the SSD ratio alone.
Water-cement ratio is a separate calculation
With 180 kg free water and 400 kg cement, water/cement = 180 ÷ 400 = 0.45. Free water includes relevant water contributions from aggregates and liquid admixture, so the amount poured separately into the mixer may be smaller.
The water-cement ratio calculator and graph lets you explore the relationship and solve for water or binder. The reference curve is a preliminary aid. Actual materials, workability, compaction, curing and testing determine the performance of a proposed mix.
Choose the calculation you need
- Concrete mix design calculator: start with grade, exposure, materials and a water/binder ratio; follow all eight calculation steps.
- Concrete volume calculator: calculate slab or footing volume from dimensions, then carry that volume into the design.
- Cement-bag calculator: scale a designed mix to the number of 50 kg cement bags available.
- Nominal mix limits: inspect the selected IS 456 Table 9 provisions for M10, M15 or M20.
Sources and scope
IS 456:2000, particularly grade designation and clause 9.3/Table 9; IS 10262:2019, ordinary/standard-grade proportioning and trials. These are BIS-authored texts on third-party hosts. Check the applicable editions, amendments and project specification through BIS.
The numerical examples are calculated from this site’s published input assumptions. No independent engineering approval is claimed. For sources, implementation boundaries and the correction process, read our methodology and the research behind the calculator.